Electrical device



Nov. 13, 1945. A, G. BUGLER ET AL. 2,388,6fi'7 ELECTRICAL DEVICES FiledOct. 12, 1943 00 O O O OQOOOQQQODOOQO lNVEN 70/25 14. 6. BUGLEE fl EH507% BY! Q HTTO/P/VE'Y Patented Nov. 13, 1945 Arthur G.

ELECTRICAL DEVICE Bugler, Hinsdale, and Herbert P.

Heath, Riverside, 111., assignors to Western Electric Company,Incorporated, New York, N. Y., a corporation of Newv York ApplicationOctober 12, 1943, Serial No. 505,942

7 Claims.

This invention relates to electrical devices and more particularly toelectrical resistance coils.

The present invention is particularly useful where a high qualityextremely compact small size resistance coil, having high resistancevalues, is necessary, such as, for example, for use in certain types ofmeter resistance coils.

An object of this invention is to produce a coil of compact small sizein a simple, inexpensive and rapid manner and resulting in a simplerigid structure of high quality.

In accordance with the above object, the present invention, in oneembodiment thereof, comprises a, small compact resistance coil withoutspoolheads, the coil being wound on a cellulose acetate tube having aninternal diameter only slightly larger than its terminal leads, theexterior of the coil being covered with cellulose acetate, and the coillead wires being connected to the terminal leads, covered with pyroxylinor coalescible acetate cement, and inserted with their connected endsdoubled back into the hollow tube, after which a similar cement is usedto seal the aperture and bond the terminal leads to the tube, as well asto the external cover.

Other objects and advantages of this invention will more fully appearfrom the following detailed description, taken in connection with theaccompanying drawing, in which Fig. 1 is a perspective view of aresistance coil embodying the features of this invention and Fig. 2 is alongitudinal central section, partly in elevation and somewhatdiagrammatic, on an enlarged scale, of the coil of Fig. 1. I

Referring to the drawing, particularly Fig. 2, Hi indicates a celluloseacetate non-conducting core tube for supporting a resistance winding llof wire which may be wound in a usual wellknown manner thereon, theinner end of the winding being secured to the tube by a strip [2 ofcellulose acetate fabric backed Scotch tape. The winding II in thepresent embodiment of the invention is an enameled nickel chromium wire.A suitable length of wire [3 is left free at its inner end outside itspoint of attachment to the tube for later splicing to a terminal lead 44in a manner to be described hereinafter. During the winding of theparticularly illustrated type of winding ll, one turn l5 of interleavinginsulation, such as cellulose acetate sheet material, is insertedbetween each layer of the winding. The outer end of the winding II isled across the outside of the winding to the end of the coil oppositethe lead wire [3 and over a strip ll of cellulose acetate fabric backedScotch tape, a

suitable length of wire I8 being left free outside of its point ofattachment to the winding for later splicing to a terminal lead [9. Asmall piece 2|] of similar tape is placed over the outer lead wire l8 onthe end of the coil between the core tube aperture and the outside ofthe winding II and is pressed smooth against the end of the coil toinsure a good bond. The tape 20 completely covers the lead wire l8between the core tube aperture and the outside of the winding, andpreferably extends over the periphery of the winding II for a shortdistance, the extreme end length of the lead wire l8 being left free anduncovered. Around the completed winding II is wrapped one turn ofinterleaving insulation, such as cellulose acetate sheet material 2|.

Spliced to the inner and outer lead wires 13 and I8, are the terminalleads l4 and I9, respectively, which are of an insulated and celluloseacetate coated and stranded type. The ends of the lead wires l3 and itare preferably wrapped a suitable number of turns around the bared orskinned ends or the terminal leads l4 and I9, respectively, or may belaid thereon in parallel arrangement, and then soldered thereto, thesplices being indicated at 23. Thereafter, the splices 23 are eachinsulated with a piece 24 of cellulose acetate fabric backed Scotch tapeand then each splice is dipped into pyroxylin or coalescible acetatecement, indicated at 25, and immediately pushed into the aperture of thecore tube Ill to the positions shown in Fig. 2, the coil lead wiresbeing doubled back into the core tube aperture. The cement 25 serves toseal the ends of the core tube aperture and coalesces and bonds theterminal leads to the wall of the aperture. Preferably, the insulationon the terminal leads I4 and i9 should extend a minimum of one-eighthinch inside the core tube aperture. It is to be understood that thelength of the free ends of the lead wires l3 and H3 is such that thepositioning of the terminal leads M and ill, as above described, will bepermitted and also provides for suflicient slack in the lead wires l3and I8, which is tucked into the core tube aperture. The core tubeaperture has a diameter only slightly larger than that of the terminalleads [4 and i9, which, in the completed core, in addition tocompactness, provides a very r id anchorage for the terminal leads.

After baking the coil at a suitable temperature and period of time in anoven and its removal therefrom and while the coil is still hot, it isbrushed with or' dipped in an insulating varnish, such as Bakelite, carebeing taken to prevent the varnish from covering the terminal leads Mand 9 for more than approximately one-quarter inch from the ends of thecoil. Thereafter, the coil is again baked at,a suitable temperature andperiod of time and then it is covered with an inner cover comprising atleast two turns of cellulose acetate sheet insulating material 26, theinner and outer ends thereof being secured with cellulose acetatecement. An outer cover 21 of cellulose acetate impregnated sheet muslinis then wrapped around the coil and both ends thereof are secured with asuitable cellulose acetate cement 28.

From the above description, it will be apparent that a compact smallsize headless electrical resistance coil is provided having highresistance values and of a simple and rigid high quality constructionwhich may be assembled in an inexpensive and rapid manner and onewherein the terminal leads spliced to the lead wires are firmly anchoredfrom pulling away from the coil and the entire coil sealed with acoalescible material.

Although the features of this invention have been described withreference to a particular type of electrical coil, such as aninductively wound resistance coil, it should be understood thatmodifications can be made and it is capable of other applications,including non-inductively wound resistance coils.

What is claimed is:

l. A coil comprising an inner tube of coalescible material, a pluralityof convolutions of wire wound on said tube, a lead wire having adiameter slightly less than the bore of said tube, a splice connectingsaid lead wire to said winding, and a covering of coalescible materialover said splice, said splice being inserted in the bore of said tubeand coalesced thereto.

2. An electrical coil comprising an inner tube of coalescible material,a plurality of convolutions of insulated wire wound on said tube, aninsulated lead wire having a coating of coalescible material and anexternal diameter slightly less than the bore of said tube, a spliceconnecting an uninsulated portion of said lead wire to an uninsulatedportion of said winding, and a covering of coalescible material oversaid splice, said splice being inserted in the bore of said tube andcoalesced thereto. I

3. An electrical coil comprising an inner tube of coalescible material,a plurality of convolutions of insulated wire wound on said tube, aninsulated lead wire having a coating of coalescible material 4 and anexternal diameter slightly less than the bore of said tube, a spliceconnecting an uninsulated portion of said lead wire to an uninsulatedend of a portion of said winding extending from an end of the coil, acovering of coalescible ma-. terial around said splice, a covering ofcoalescible cement over said covered splice, said splice'being insertedin the bore of said tube and coalesced thereto, and a covering ofcoalescible cement on I the end of the coil surrounding the coated leadwire to seal and further anchor the splice in the bore of the tube.

4. An electrical coil comprising an inner tube of coalescible material,a plurality of convolutions of insulated wire wound on said tube, aninsulated lead wire having a coating of coalescible mat'erial and anexternal diameter slightly less than the bore of said tube, a spliceconnecting an uninsulated end of said lead wire to an uninsulated endportion of said winding extending outwardly from an end of the coil, acovering of coalescible cement over said splice, said splice beinginserted in the bore of said tube and coalesced thereto, an end portionof the wire being doubled back into the bore of the tube and lyingagainst the end of the coil, a cover of cellulose acetate materialaround the coil, and a covering of coalescible cement on the end of thecoil for sealing and bonding the coated lead wire, the outer portion ofthe winding wire and said cover together and to the coil end.

5. An electrical coil comprising an inner tube of coalescible material,a plurality of convolutions of wire wound on said tube, a lead wirehaving a diameter slightly less than the bore of said tube, a spliceconnecting said lead wire to an outer convolution of said winding, thewinding wire being extended across the periphery of the winding to anend of the coil, extending therefrom and spliced at its end to said leadwire, a covering of coalescible cement over said splice, said splicebeing inserted in the bore of said tube and coalesced thereto, and anend portion of the wire bein doubled back into the bore of the tube andlying against the end of the coil.

6. An electrical coil comprising an inner tube of coalescible material,a plurality of convolutions of wire wound on said tube, a lead wirehaving a diameter slightly less than the bore of said tube, a spliceconnecting said lead wire to an outer convolution of said winding, thewinding wire beiig extended across the periphery of the winding to anend of the coil, extending therefrom and spliced at its end to said leadwire, coalescible material under said wire extending across theperiphery of the coil, a covering of coalescible cement over saidsplice, said splice being inserted in the bore of said tube andcoalesced hereto, an end portion of the wire being doubled back intothebore of the tube and lying against the end of the coil, coalesciblematerial over said latter portion of the wire extending from the bore ofthe tube to and along the periphery of the coil for a distance, and acovering of coalescible cement on the end of the coil for sealing andbonding the lead wire, coalescible material, and said latter portion ofthe wire to the coil end.

7. An electrical coil comprising an inner tube of coalescible material,a plurality of convolutions of insulated wire wound on said tube,insulated lead wires having a coating of coalescible material and anexternal diameter slightly less than the bore of said tube forconnection to inner and outer ends of said winding, splices connectinguninsulated portions of said lead wires to uninsulated portions of saidwinding, coverings of coalescible material over said splices, saidsplices being inserted in opposite ends of the bore of said tube andcoalesced thereto, end portions of said winding ends being doubled backinto the bore of the tube and lying against the ends of the coil, andcoverings of coalescible cement on the ends of the coil surrounding thecoated lead wires to seal and further anchor the splices in the bore ofthe tube.

ARTHUR G. BUGLERL. HERBERT P. HEATH.

